A prospective, non-concurrent study is proposed by which to compare rates, types and patterns of health services utilized by two groups of Medicaid children: one group will have received preventive health screening under the State of Maryland's Early and Periodic Screening, Diagnosis and Treatment (EPSDT) program in the first quarter of fiscal year 1977, and a comparable group of children remain unscreened. The EPSDT-screened group will be further sub-grouped into those found to have positive and negative results at screening, thus allowing some statistical control for health status. Health services utilized and health service costs incurred by the respective groups for the duration of one year will be analyzed and compared. Multivariate analysis will be used to determine if health service events and related costs can be predicted from the variables available to this study, for the ultimate aim of developing predictive models of health service utilization patterns among low-income populations. The purpose of the study is: (1) to describe the State of Maryland's EPSDT program in terms of the population being served and prevalence of conditions being detected, the latter assumed to reflect unmet health needs in a childhood population; (2) to assess the impact of a prescriptive screening program upon the utilization of health services by poor children, and its effects upon related service costs; and (3) to develop from routine state data sources, in effect for fiscal accountability purposes, baseline data for projection of health resource needs and costs.